Microdevices, such as integrated electronic circuits and microelectromechanical system (MEMS) are used in a variety of products, from automobiles to microwaves to personal computers. Designing and fabricating microdevices typically involves many steps, known as a “design flow.” The particular steps of a design flow often are dependent upon the type of microcircuit being designed, its complexity, the design team, and the microcircuit fabricator or foundry that will manufacture the microcircuit. For example, if the microdevice is a complex integrated circuit, then various software and hardware “tools” typically will be used to verify the device's design prior to manufacture, to confirm that the manufactured circuit will operate as intended.
During the microdevice design flow process, a physical design for the device will be created describing the specific geometric elements that will make up the device. This type of design often is referred to as a “layout” design. For example, if the microdevice is an integrated circuit, then the geometric elements will define the shapes that will be created in various materials to actually manufacture the circuit device components (e.g., contacts, gates, interconnect lines, etc.) making up the circuit. While the geometric elements may have any desired shapes, such as circular and elliptical shapes, they typically will be polygons. Layout tools (often referred to as “place and route” tools), such as Mentor Graphics' IC Station or Cadence's Virtuoso, are commonly used for both of these tasks.
After the layout design has been finalized, it is converted into a format that can be employed to manufacture the microdevice. For example, the microdevice may be manufactured using a photolithographic manufacturing process. With this manufacturing process, the layout design data will be converted into a format that can be used by a mask writing tool to create a mask for use in a photolithographic manufacturing process. Masks are typically made using tools that expose a blank mask substrate to a beam of radiation, such as an electron or laser beam, to create opaque, translucent or transparent patterns. Alternately, the microdevice may be manufactured by using a beam of radiation to directly write patterns onto a device substrate, by, for example, energizing portions of a resist material formed over the substrate's surface prior to an etching process. With this type of direct-write manufacturing process, the layout design data similarly will be converted into a format that can be used by a radiation beam tool to write the desired patterns onto a substrate.
Most radiation beam writing tools are able to only write certain kinds of polygons, however, such as right triangles, rectangles or other trapezoids. Moreover, the sizes of the polygons are limited physically by the maximum beam aperture size available to the radiation beam writing tool. Accordingly, larger geometric elements in a layout design, or geometric elements that are not basic right triangles, rectangles or trapezoids (which typically is a majority of the geometric elements in a layout design) are “fractured” into smaller, more basic “atomic” polygons that can be written by radiation beam writing tool. Typically, these atomic polygons will be rectangles. Once the layout design has been fractured into atomic shapes, the layout design data can be converted to a format compatible with a particular radiation beam writing tool. Examples of such formats are MEBES, for raster scanning machines manufactured by ETEC, an Applied Materials Company, the “.MIC” format from Micronics AB in Sweden, and various vector scan formats for Nuflare, JEOL, and Hitachi machines, such as VSB12 or VSB12.
With conventional radiation beam writing tools, each atomic shape may be formed with a single beam exposure through one or more apertures that are configured for the desired atomic shape. This exposure is often referred to as a “shot.” The operating time of radiation beam writing tool typically will be proportional to the number of shots required to write the desired pattern. Accordingly, as microdevice designs become more complex, the amount of time required to create a photolithographic mask or manufacture a microdevice using a direct-writing technique has increased. Further, with photolithographic manufacturing, some resolution enhancement techniques used to improve the manufacturing process, such as optical process correction (OPC), have dramatically increased the number of atomic shapes in fractured layout designs. As a result, creating a set of photolithographic masks required to manufacture an integrated circuit microdevice may cost millions of dollars.